The present invention relates to a chip-type composite part in which passive elements (a capacitor, resistor, inductor, etc.) are formed on a single substrate.
As is well known, in a composite part, passive elements such as a capacitor, resistor, inductor, etc. are combined and arranged on an insulating substrate to produce a compact part. In general, a capacitor-resistor combination and a capacitor-inductor combination are very common, and a resistor-inductor combination is rare. Among those combinations, the capacitor-resistor combination, called a CR composite part, is most commonly used.
FIG. 6 (sectional view) and FIG. 7 (perspective view showing an appearance) illustrate a structure of an example of the CR composite part. In this CR composite part, a resistor portion R and a capacitor portion C are formed on the front surface and the back surface of an insulating substrate 30, respectively. The resistor portion R is constituted of a pair of resistor electrodes 31, 32, a resistor layer 33 that is formed so as to connect the electrodes 31 and 32, and an overcoat layer 34 to cover the resistor layer 33.
On the other hand, the capacitor portion C is formed by sequentially laying a bottom capacitor electrode 35, a dielectric layer 36 and a top capacitor electrode 37, and then covering these layers by an overcoat layer 38.
Further, an outer electrode 39 for electrically connecting the resistor electrode 31 and the top capacitor electrode 37 and another outer electrode 40 for electrically connecting the resistor electrode 32 and the bottom capacitor electrode 35 are formed on end faces of the insulating substrate 30.
This type of composite part is generally produced such that the resistor portion R and the capacitor portion C are formed, by printing and firing, on the respective surfaces (i.e., front and back surfaces) of the insulating substrate 30. Therefore, it is difficult to control the quality of this type of composite part because cracks etc. are likely to occur in the latter-formed passive element (resistor portion R or capacitor portion C). In addition, since passive elements are formed on both surfaces of the insulating substrate 30, neither surfaces of the composite part are flat, which results in inferior mounting efficiency. Further, since both surfaces need to be protected, the composite parts cannot be laid one on another without using some jigs etc. This is a problem in handling the composite parts.
FIG. 8 shows another type of CR composite part in which a resistor portion R and a capacitor portion C are formed in series on an insulating substrate 50. FIG. 9 shows an equivalent circuit thereof.
Since in this type of CR composite part the resistor portion R and the capacitor portion C cannot be measured separately after the formation of the passive elements, an impedance decomposition technique (decomposition of the resistance and capacitance components) is needed. This will need a long measurement time, so that the productivity is reduced.